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See Lawson's notes

  • Should we transfuse someone Hb 65 g/L? Answer: it depends. When did she start bleeding?
    • Bleed acutely - Hb normal. Bleed chronically - Hb low as you pull fluid into the circulation
    • Could be more or less dire - depends on her volume status
    • If shocked, unwell, continuing to bleed --> transfuse
    • Chronic peptic ulcer - gastroenterologist won't see them if Hb low
  • Transfuse people to give them oxygen carrying capacity
  • Complications of transfusion
    • Volume overload
    • Blood borne viruses - HIV (<1/10 million), hep B, hep C, malaria, bacterial. Risk unquantifiable. Bacterial most common (because of skin organisms)
    • Reactions
      • Red cell antibody reactions (ABO reactions - acute hemolysis)
      • Delayed reactions
      • Febrile, nonhemolytic transfusion reactions (HLA antibodies against contaminating white cells - less common because the blood is filtered)
  • We'd give her packed red cells (save the other products for other people; also avoids fluid overload)
    • Donating blood: packed red cells, platelets and plasma
  • If you get the blood group right, you're probably not going to kill them. If you get it wrong, you probably will.
    • Lyse the red cells --> set off complement --> deposit in kidneys --> bad news.
  • Rh group: D, C/c or E/e - antibodies can be acquired
  • Don't match for Kid or Duffy
    • These minor blood groups are not terribly antigenic
  • Donated blood has a 6 week expiry date
  • If blood gets warm --> hemolysis. If bacteria are in it --> multiply. >30 mins outside the fridge -- throw it out.
  • Need to be able to track the unit (275mL) of blood --> inventory management
  • Blood products are safer where donation is voluntary and not paid.

Cutoff for transfusion

  • Hb <70 g/L: need a good reason NOT TO transfuse
  • Hb >100: need a good reason TO transfuse (e.g. thalassemia, they'll not make good rbcs)
  • within the highlight region (68-100), individual patient factors determine whether we transfuse

Different Forms of Replacement Therapy

  • Packed red cells.
  • Platelets.
  • Fresh frozen plasma.
  • Cryoprecipitate.
  • Purified protein products (factor concentrates, albumin, Ig).


Case

  • M/24 motor vehicle accident
    • shocked, hypotensive, major orthopedic and intra-abdominal trauma
  • what blood products? crossmatched? what tests?
  1. resuscitate with whole blood (can't give AB plasma to everyone - because there aren't enough people with this blood type - worth the time to give him the right type of blood). Worth the investment of time in collecting blood
    • just give saline/colloid/crystalloid to get BP up
  2. give O- red cells (can give O+ to men). Give these until you've got blood group, then switch to the right one
  3. collect blood, blood group (takes a minute)
  4. give the right type of plasma
  5. give the right type of red cells
  • don't overuse plasma - it can have antibodies we don't always predict (e.g. TRALI - completely unpredictable). Bad if you're well, much worse if you're shocked.
    • TRALI is a potentially fatal complication of transfusion

FFP

  • Indications
    • specific therapy (vitamin K, factor concentrate) not appropriate or available
    • correct DIC
    • resuscitate people

Cryoprecipitate

  • scum on bottom of FFP when you thaw it
  • rich source of
    • factor 8
    • fibrinogen
    • factor 13
    • vWF
    • fibronectin

Platelets

  • die if you cool them too much; so they can contain bacteria - stored at room temperature; short shelf life
    • so platelet supply is a problem
  • indication:
    • bleeding
    • operation
    • bone marrow failure
    • surgery/invasive procedure
    • platelet function disorders
  • give prophylactic platelets depending on circumstances

Case

  • F/55
  • elective open cholecystectomy
  • intern ruptures spleen, needs blood NOW
  • blood should be group/screened before the surgery
    • blood bank will send it in an air tube

Crossmatching

  • mix together and see if they clag

Selection of the correct unit for transfusion

  • ABO and Rh(D) group of the recipient.
  • Red cell antibody screen on the recipient:
    • Negative Ab screen – electronic crossmatch to be performed.
    • Positive Ab screen – antibody identification and serological crossmatch.
  • Check for previous records and compare – confirm blood group and previously detected red cell antibodies.
  • 72 hour rule: transfusion or pregnancy within three months.
    • might be in the process of making an antibody that you haven't detected
  • don't give Rh- blood to Rh+ recipient
  • group and screen
    • if you've not had a transfusion and you're a guy - you probably don't have anyhting other than anti-A and anti-B
    • occasionally women who have had kids before, or you've been transfused, you may have non-ABO antibodies
    • only 1% of population have anything other than ABO antibodies
    • group and screen - check to make sure they're one of the 99% who don't have antibodies to stuff other than ABO
  • for thalassemia patients (who are transfused all the time), we need to know all their different antibodies. But for just one off, you just check that you can use group-specific blood.
  • A and O most common, people have antibodies to the group that they're not

Antibody/antigen reactions

  • Mix the antigen-containing cells from patient with antibodies to various things (A, B, D). They'll clag if there's a positive reaction, to tell you what their type is.
    • then you use test cells with their plasma, to check you've done it right
  • Cells sink if the reaction doesn't happen. Cells float if reaction does happen
  • If you have 3 people who between them contain all of the antigens, you can use it as a quick test whether there are any antibodies (99% of people won't). This lets you screen as to whether you need to do more work.
  • Then you can use greater batteries of antigens in particular peoples' blood
  • This is much cheaper than doing molecular tests on everyone